All prior art endodontic file systems consist of either a landed rotary file or a non-landed rotary file. Landed rotary files are considered safer but less efficient than non-landed rotary files. Non-landed rotary files are considered more efficient but also more susceptible to procedural mishaps.
The radial lands of a landed rotary file keep the file centered in the root canal and help the file follow the natural canal anatomy. Therefore, when the file passes through the apical foramen of the canal, the file does not transport or destroy the natural apical anatomy. However, the file is less efficient at cutting because the radial lands prepare the canal in a planing motion. The landed file also has less flexibility leading to increased risk of file separation resulting in pre-mature loss of the tooth.
A non-landed file, while cutting more efficiently and having greater flexibility than a landed file, does not naturally stay centered in the root canal. Therefore, it can transport or straighten curved root canals. Further, when non-landed files of medium to large size (i.e., size 20 mm or greater) pass through the apical foramen of the canal, the files can transport the natural position of the apical foramen and rip the apical foramen. This transportation and ripping of the apical foramen leads to difficulty in filling the root canal and can lead to overfilling the root canal resulting in pre-mature tooth loss.